Pattern



2 She'cs-SheexI 1 PATTERN mVENToR. EwHZa/z/Z,

E. H. ZAHN De@a 13, 1949 Filed July 22, 1944 E. H. zAHN 2,491,146

PATTERN 2 Sheets-Sheet 2 Dec. 13, 1949 Filed July 22, 1944 A INVENTOR.ifm JY Z'az.

Patented Dec. 13, 1949 2,491,146 PATTERN Eric n. zalm, round Ridge, N.

Laboratories,

Austenal Y., assignor to`A Incorporated, New

York, N. Y., a corporation ot New York Application July 22, 1944, SerialNo. 546,160

Claims. (Ci. 22-163) This invention relates, in general, to the `art ofcasting, and has particular relation to an improved pattern.

One of the main objects of the present invention is to provide animproved pattern for forming a casting cavity in a refractory mold,which pattern is collapsible for removal from the mold and adapted forrepeated use.

Another'object of the invention is 4to provide a collapsible patterncomposed of a relatively tough material resistant to wear and to theconstituents of the refractory mold material and to the abrasivecharacter of such material and self-parting relative to the moldmaterial; more particularly, a hollow collapsible pattern cornposed ofrubber or rubber-like material.

Another object of the invention is to provide a pattern which iscollapsible to an extent to permit removal from an undercut moldwithout'the necessity of making the mold of multi-section constructionto permit removal of the pattern; also without requiring taper or draftin the mold for removal of the pattern.

Another object of the invention is to provide means for maintainingduring formation of the refractory mold the hollow collapsible patternshaped to -form a casting cavity corresponding to the article to beproduced, and means for collapsing the pattern for removal from themold.

Further objects and advantages of the invention will appear from thefollowing detailed description, taken in connection with theaccompanying drawings in which:-

Figure 1 is a side elevational view of one simplifled and illustrativeform of master pattern showing same applied to an insert for forming themold cavity in which the collapsible pattern is produced;

Figure 2 is an end view of the insert shown ln Figure 1;

Figure 3 isa sectional view of the insert which is placed in the moldcavity formed by the master pattern and insert shown in Figures 1 and 2for completing the conguration of the mold cavity and imparting thehollow form to the collapsible pattern;

Figure 4 is an end view of the insert shown in Figure 3;

Figure 5 is a sectional view showing the mold produced from the patternand insert of Figures 1 and 2, with the insert of Figures 3 and 4 inplace for imparting the hollow form to the collapsible pattern;

Figure 6 is a top plan view showing the hollow pattern and vIl() pliedto the refractory the mold cavity the metal, alloy or other materialcollapsible pattern applied to an insert for main- 2 .Y shaped to form acasting to the article to be protaining the pattern cavity correspondingduced; Figure 7 is a sectional view showing, in more or rless simplifiedform, the step of forming the refractory mold from the hollowcollapsible' pattern; v

Figure 8 shows the step ofcollapsing the tern for removal from therefractory mold;

Figure 9 is a side elevational view o f the hollow flexible pattern forforming the crucible;

Figure 10 is a top plan view of the pattern shown in Figure 9;

Figure 11 is al sectional of forming the crucible; and p Figure 12 showsthe crucible of Figure 11 apmold for introducing into view showing thestep having the desired properties for the nished casting. 4

Referring to the drawings, the master pattern 5 is shaped to theconfiguration of the article to be produced, and detail of such article.It may be formed of metal,- alloy or other suitable material, and infact may be an actual specimen of the cast metal article.

The shape of the patterni will vary according to thearticle to be cast.The particular master pattern selected for illustration is in the formof a concave worm Wheel, pinion, cog wheel or the like, having an axialopening 6 provided with agroove or key-way 1. The insert 8 has a anerzor head at 9 and a shaft I0 which removably ts the opening 6 and isprovided with a key or spline II fitting the groove or key-way l. Thepattern Y 5 and insert 8 preferably have a high degree of surfacesmoothness and are otherwise of a character to impart a high degree ofsmoothness to the molding surfaces of the mold sections formed aboutpattern 5 and insert 8.

In the practice of my invention I form a sectional mold about thepattern 5, for example, in

the manner more fully disclosed in Patent No;

2,306,516, issued December 29, 1942, to Eric H. Zahn, and in thecopending application of Eric H. Zahn, Serial No. 524,025, filedFebruary 26, 1944, now Patent 2,459,402 issuedv January 18,

1949. The resulting sectional mold comprises, as

shown in Figure 5, mold sectionslZ and I3 composed of any suitablematerial-preferably a low fusing alloy, such as a tin-bismuth alloy-asmore fully described in the Zahn patent above mentioned. The moldsections I2 and I3 are preferably reinforced by outer reinforcing'flasks or` mold parts Il and I5 composed. for example, of

preferably follows all ne' 8 and insert 8 are removed. leaving a moldcavity shaped at I6 to the configuration of the article to`be` producedand following all une detail of the master pattern.

The next step is to form the hollow collapsible sub-master pattern inthe sectional 'mold 'I2, I3. In accomplishing this, the mold sections I2and I3 are placed together, with the insert I8 disposed', as shown inFigure 5, in the cavity I8 formed bythe master mold 8 and insert 8. Theinsert I8 (Figures 3 and 4)', which is preferably formed of metal andhas a high degree of surface smoothness, has its base (Figure lsupportedin the cavity portion I9 formed by the base of the insert' 8. Insert I8has an extending annular portion I9' for imparting the hollow form tothe collapsible pattern, and an extending shaft part 28 provided with akey or spline 2| for forming in the collapsible pattern an openingcorresponding I to the opening 8 in the master pattern anda groove orkey-way corresponding to the groove or key-way 1 in the master pattern.

The mold sections I2 and I3 are preferably provided with locating orpositioning dowels or other suitable means (not shownl' for assuringaccurate positioning of the mold sections relative to each other. Withthe insert I8 in place in o'ne 4 v resistant-to the abrasive characterof the fractory mold material and self-parting relative to suchmaterial. The pattern is of a character to give a high degree of surfacesmoothness and detail to the casting surface of the refractory mold. Thearticles produced in the mold cavity formed by the pattern 28 are castwith a high degree of surface smoothness and detail, and requirelittleif any, hing of the articles after the casting operatic Thepattern 28 is used to produce the refractory mold, for example, byapplying it to an insert 28 which has a base 29 and an extending annularpart 38 ntting: the, hollow interior of the pattern 28 to maintain thepattern shaped to form a casting cavity `orresponding to the article tobe cast.

, Air holes or vents may be provided at 3I for assuring that the hollowinterior of the pattern 28 conforms snugly to the insert 28. A heatresisting frame or investment .,nask 32 is applied and lo- 'catedrelative to the insert 28, for example, by-

' positioning or locating dowels 33.

mold section, the cavity I6 of this section and the cavity I6 of theother section may be filled, as far as possible, with a suitable rubberor rubber compound in an uncured condition. Upon placing the moldsections I2 and I3 together, they are held tightly and securelytogether, preferably under pressure. If desired, with the mold sectionsI2 and I3 held together, the mold cavity may be further nlled by forcingrubber or rubber compound through opening 24 so as to expel, as far aspossible, all air from themold cavity.

Thereafter, and with the mold sections I2 and I3 held together,preferably under pressure, un-

cured rubber, rubber compound, latex or other suitable rubber orrubber-like material, natural or synthetic, is injected under pressureinto the mold cavity I8 through the opening 24, andthe rubber orrubber-like material is cured preferably while the pressure ismaintained. The rubber or rubber-like material is of vsuch characterthat it will cure at a temperature below that which will soften orotherwise deleteriously affect the mold sections I2 and I3.

By curing the rubber or rubber-like material while maintaining it underpressure I assure that vThe frame 32 is then filled, through the opening34, with a wet mix of refractory investment 'material which may be anyknown or other suitable investment material such, for example, as theplastic mix disclosed in the copending application of Paul F. Collins,Serial No. 450,619, i'lled July 1, 1942, now Patent 2,380,945 issuedAugust 7, 1945. The wet or plastic mix is 'preferably packed tightly,for example, by vibration, against the surface of the pattern 28,-and isthen permitted to set to form the rigid and self-sustaining or bondedrefractory mold 35.

The insert 28 is then removed and a plate 38 is applied, as shown inFigure 8, this plate being positioned relative to frame 32 by -thelocating dowels 33. The plate 38 has an opening 39 which opens into thehollow interior 40 (Figure 8) of the pattern 26. By applying, forexample, a hose connection 4I to a vacuum pump (not shown) the hollowinterior of the pattern 26 may be evacuated or the pressure thereinreduced suiliciently to cause the pattern to collapse for removal fromthe mold 35, notwithstanding the undercut character of the mold due tothe concave form of the periphery of the pattern. The pattern 26 maythen be again applied to insert 28 and used for making furtherrefractory molds.

the mold cavity is completely filled, and thereby produce a hollowcollapsible sub-master pattern 26 shaped externally to the conngurationand 'following all iine detail of the article to be produced. The mold.sections I2 and I3 are then separated, whereupon the pattern 26 andinsert I8 are removed and the pattern 26 may then be removed from theinsert I8. The sprue element may be cut off flush with the end of thepattern 28, and the hollow collapsible pattern is then ready for use.

The resulting hollow collapsible pattern 26 of rubber or rubber-likematerial is adapted for` repeated use. which avoids the necessity ofmaking a new pattern for each new refractory mold as required where apattern formed, for example, of wax is employed. The pattern 28 istough, resistant to wear and to the constituents of the refractoryinvestment material forming the bonded refractory mold or mold part, andis also Due to its resilient character the surface of the patternagainst which the refractory mold is formed will, after collapse ordistortion, spring back to the configuration for accurately producingthe desired article.

In the particular embodiment of the invention selected for illustration,a hollow collapsible pattern 48 (Figures 9 and 10) is formed generallyin the manner and preferably of the material described in connectionwith, the formation of the hollow collapsible pattern 26.

The hollow collapsible pattern 46 is applied to an insert 48 which has abase 49 and an extending part 50 fitting the hollow interior of thepattern 46 to maintain pattern 46 shaped to form the desired moltenmetal receiving or pouring opening 52 in the crucible 53. An air hole orvent may be provided at 54 for assuring that the pattern 46 conformssnugly to the insert 48. A heat resisting frame or investment flask 56is applied and located relative to the insert 48, for example, bypositioning or locating dowels 58. A plate 60 may be applied to theframe 56 as shown in Figure 11.

The frame 88 is then filled, through the opening 62, with a wet mix ofrefractory investment material, which may be any known or other suitableinvestment material, such, for example, as the plastic mix referred toin connection with the formation of the refractory mold part 35. Therefractory crucible part 63 may, for example, be introduced through theopening 64 in the plate 60. 'I'he Wet or plastic mix is preferablypacked tightly, for example, by vibration, in contact with the hollowcollapsible pattern 46 and is then permitted to set to form the rigidand self-sustaining or bonded crucible 53 with its crucible part 63. Theinsert 48 and plate 60 are then removed,

i whereupon the pattern 46 may be collapsed and withdrawn and thecrucible 53, with its crucible part 63 applied to the refractory mold35,-as shown in Figure 12.

While I have described the crucible 53 as poured separately from themold 35, it is to be understood that the crucible may be poured againstthe mold, or the mold poured against the crucible, if desired; thus toassure accurate fit and conformity between the refractory mold 35 andthe crucible 53.

Upon application of the crucible 53 to the refractory mold 35, metal,such as a cobalt-chromium alloy or other high fusing metal or alloy, orother material having the desired properties for the finished casting,is poured or otherwise introduced into the mold cavity 1.0 (Figure 12)through the opening 52 in the crucible. If de-l sired, vacuum may beapplied to the opening 34 in the frame 32 (Figure 12), and thus throughthe relatively porous body of the refractoryA mold 35 to draw the moltenmetal into the mold and thus assure complete filling of all detailedformations of the mold cavity 10. The resulting cast-l ing, which mayhave' extreme hardness and be diilicult to machine, has smoothness anddetail, and requires little, if any, finishing of the article after thecasting opera- After the casting has been made, the refractory mold 35may be broken to permit removal of the casting, as well understood inthe art.

I do not intend to be limited to the precise details or to the preciseembodiment of the invention shown and described, as variations inthedetails and other embodiments are contemplated within the scope of theappended claims.

I claim:

1. A pattern for forming in a relatively rigid and unitary mold body, amold cavity having a a high degree of surface molding surface along thesides and inner end of the cavity with an undercut formation in thesurface of the cavity and an opening leading v from the mold cavity tothe exterior of the mold body, said pattern comprising a rigid insert,and an outer resilient member of hollow form and of a charactercompletely to cover the sides and inner end of said insert and having anopening leading from its hollow interior for insertion of 'sert from theresilient member, sufficient to free the undercut formation on theresilient member from the undercut formation in the surface of the moldcavity for separate removal of said resilient member from the moldcavity.

2. A core according to claim 1 wherein the outer resilient memberconsists essentially throughout its thickness of rubber-like material,with the inner surface of the rubber-like material cooperating directlywith the rigid insert and the outer surface of rubber-like materialpresented directly to the surface of the mold cavity.

3. A core according to claim 1 wherein the rigid insert consistsessentially of metal.

4. A core according to claim 1 wherein there is a base carried by therigid insert and of a character to close the adjacent open side of aninvestment flask in forming the mold body.

5. A core according to claim 1 wherein the rigid insert has at least onevent opening of a character to lead from theA place ofy cooperation ofthe inner surface of the resilient member with the outer surface oi theinsert and through said rigid insert to the exterior thereof.

' ,ERIC H.- ZAHN.

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Gronemeyer et al. -vNov. 12, 1946

